WATER QUALITY OF CRYSTALLINE ROCK AQUIFERS IN NEW ENGLAND

Abstract:

The U.S. Geological Survey National Water-Quality Assessment (NAWQA) program is conducting regional assessments of ground-water quality conditions by targeting 19 principal aquifers nationally that are major sources of both public- and domestic-supply drinking water. Sixteen of these principal aquifers, including crystalline rock aquifers in the six New England states, are currently being assessed by the NAWQA program. The objective of this study is to evaluate factors that relate to the occurrence of natural and anthropogenic contaminants in crystalline-rock ground water in the context of a regional lithochemical, land-use, and hydro-structural framework.

Water-quality data for regulated contaminants (arsenic, nitrate, chloroform, nitrate, and methyl tert-butyl ether) and unregulated compounds (chloride, fluoride, iron, and manganese) collected from 1997 to 2007 as part of the U.S. Environmental Protection Agency's Safe Drinking-Water Act (SDWA) Program will be used in the regional assessment. Untreated ground-water samples have been compiled from 4,750 individual public-supply drinking-water wells completed in crystalline rock aquifers in Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island, and Vermont. In complementary NAWQA studies, ground-water samples were collected from 117 domestic-supply wells completed in crystalline rock aquifers in the region during the same period 1997 to 2007 and analyzed for a wide variety of water-quality constituents: pH, specific conductance, dissolved oxygen, temperature, nutrients, major ions, trace elements, radon-222 gas, radium species, recharge-age tracers, pesticides, and volatile organic compounds. Using results from both the SDWA and NAWQA programs, we will describe the important regional scale controls, such as geology, lithochemistry, and land use affecting the studied contaminants.